My first cockatiel growing up was clipped when we got her until we decided to let her wings grow out. She flew a little wonky, and it gradually got worse with age and she eventually couldn't fly anymore. Our other cockatiel, who was her mate, could fly just fine, but he stayed with her all the time anyways. It was sweet.
I originally wanted Puck to be flighted, but he already has serious attitude problems, so I'm not sure that it would be in my best interest to clip him! I also like being able to take him outside. He's so heavy (muscles) that I can't imagine a gust of wind taking him away.
When I got him 3 months ago he was over-clipped, so he can't really glide either. He can jump/flap about a foot off the ground if he tries really hard. I'm careful of him falling, because he falls like a rock! I can't wait for his feathers to grow out so I can have him properly clipped.
When I took him to the vet for the first time, I had his nails and beak trimmed, and some blood drawn for a blood panel. His little wing was sore from getting blood drawn because he struggled so much! The vet took me into the other room to do it, so he didn't get mad at me. The poor baby was showing me his hurt wing hours later! I took him for a cautionary visit after he acted weird (turns out he was just acting weird), and the vet kept him for observation for a couple hours. He was VERY stressed from that too, even though no blood was drawn or anything! He doesn't enjoy the vet. D: